heterocyst present in nostoc is specialised for

1. fragmentation
2. nitrogen fixation
3. storage
4. photosynthesis

heterocyst present in nostoc is specialised for nitrogen fixation.the heterocyst are intercalary and posses a very thick outer wall each heterocyst is connected with vegetative cells on two sides through the prominent pores in the wall which later on are occupied by a refractive cynophycean granule called polar nodule.